Electric cable



Feb. 1'1, 1947. G, M HAWLTON 2,415,486

ELECTRIC CABLE Filed June 26, 1942 3 @waff/zw y ma/c G'e orge lonlfyHaJniZtan Patented Feb. 11, 1947 ELECTRIC CABLE George Monty Hamilton,

signor to Callenderl Limited. London,

Company comp!!! London, England, as-

Cable Construction England, a British .application June ze, 1942, semi No. 448,551 1n Great Braam August 21, 1941 4 Claims.

This invention relates to electric cables constructed so as to have suflicient buoyancy to float in water and particularly those adapted for carrying relatively large currents.

The usual combination of a conductor with an insulating covering has a density much greater than water, so that some additional element of low average density must be added to the cable structure to produce a buoyant cable. This has been done by making the conductor (consisting of a number of wires stranded or braided) occupy the outer part of the cable forming a tubular layer, within which is located a body of low average density, which is in the form of a cellular core. The present invention is concerned with this type of cable, in which the core is formed mainly of soft cellular rubber but having at intervals rigid parts, which serve to define the outer boundary of the core by acting as a support on or over which the wires of' the conductor lie. These rigid parts may, for instance, be discs of wood or short cylinders of cellular hard rubber (ebonite).

In accordance with the invention a. buoyant core of the kind indicated is enclosed in a tubular envelope of rubber, which, on vulcanising, joins up with the cellular rubber and forms a close fitting and adherent skin thereon. It also bridges over the rigid parts of the core and forms a continuous outer tubular layer. This layer reinforces the gas-retaining properties of the cellular material and also makes an integral enclosure of the composite core. Accordingly, the possibility and speed of deflation of the cells of soft rubber is minimised and, at the same time, the movement of water along the core, when the exterior part of the cable has suiered local damage, is limited, so that the cable retains buoyancy after such injury.

The invention will be further explained by the aid of the accompanying drawing, which shows by way of example one form of construction in accordance with the invention.

Figure 1 is a longitudinal section and Figure 2 is a transverse section on II-II of Figure l.

In these iigures the parts are not to scale; it has been necessary to exaggerate the thickness of some of the layers in order to show them clearly.

In this example the core consists of cylinders l of soft cellular rubber with thin discs 2 of wood between them. These cylinders and discs are held together, for the purpose of the assembly of the core and other parts of the cable, by

the l une four longitudinally disposed tapes 3 which are of rubberised fabric and are stuck on to the cylinders by the aid of rubber solution. Over this core is applied tubular envelope l formed of helically wrapped rubber tape, which is put on with a wide overlap (for instance. Sil-70%) so as to give the effect of two or more layers of rubber throughout the covering, stance, on a large cable have a thickness oi' about 60 mils. A rubberised fabric tape 5 is helically wrapped over the rubber 4 and over this fabric tape is stranded the conductor formed of wires 8, the whole is enclosed in a rubber covering l.

The presence of the `fabric tape 5 reduces the disturbance of the smoothness of the rubber errvelope 4 by the conductor wires during application or during the subsequent vulcanisation.

The rubber envelope may also be formed as a complete tube by extrusion over the core. In either case this envelope 4 should be applied with some circumferential tension so as to compress slightly the soft cellular core pieces I which are initially somewhat larger in diameter than the rigid pieces 2. This helps to secure a close bond between the cellular rubber i and the covering l.

The rubber envelope 4 is vulcanised on the core, preferably after the conductor 8 and the outer rubber insulating sheath 1 has been applied.

During this vulcanisation the union between the rubber envelope and the core and between the several turns and layers of the covering takes place. To facilitate this union, the envelope l should be made of a good seaming rubber compound and other well known precautions should be taken to assist the action or avoid introducing any obstacle to it.

What I claim as my invention is:

l. In a buoyant electric cable having the conductcr wires in the outer part of the cable surrounding a core body of low density and enclosed by an insulating and water-excluding sheath, a core body comprising soft cellular rubber elements combined with rigid members which define at intervals the outer boundary of the core body, the rigid members being substantially shorter than t-he soft cellular rubber elements in the f direction of the cable axis, and a tubular envelope of vulcanised rubber closely surrounding the said core body and adhering to the cellular rubber thereof.

2. In a buoyant electric cable having the conductcr wires in the outer part surrounding a core body of low density and enclosed by an insulating and water-excluding sheath, a core body comprising cylinders of soft cellular rubber having interwhich may, for in 3 posed at intervals thin rigid discs defining the outer boundary of the core body, a tubular rubber envelope closely surrounding the said core body and a mapping of rubberised fabric tape surrounding said envelope, the tape, envelope and cellular rubber cylinders being united by vul- -canisation whereby to provide a, closely( fltting adherent skin on the cellular rubber.

3. A buoyant electric cable comprising an an'- nular ilexible conductor, an insulating water-excluding sheath surrounding the conductor, a core substantially illling the space` within the conductor, said core including relatively short lengths i of soft cellular material composed of gas filled closed cells and rigid means for supporting the conductor, and a. relatively gas impermeable tubular envelope surrounding the core length and supporting means inside the conductor.

4. In a buoyant electric cable having the conductorvwires in the outer part of the cable sur- 4 rounding a core body oi' low density and enclosed by an insulating and water-excluding sheath, nv

core body comprising sott cellular rubber elements combined with rigid members which denne at intervals the outer boundary ot the core body, and a tubular envelope of vulcanized rubber closely surrounding the said core body and adhering to the cellular rubber thereof.

GEORGE MONTY HAMILTON.

REFERENCES CITED The following references are of record. in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,186,793 Wodtke Jan. 9, 1940 l2,396,269 Gooding Mar. 12, 1946 1,977,209 Sargent 'Oct. 16, 1934 Wodtke Jan. 9, 1940 

